The line record [L] holds the metadata information that applies to its corresponding sub-line [SL] records.
Record type identifier.
The counter starts at 1, and it increments sequentially by one unit.
Specifies the merchant account name.
If the column shows
A merchant reference, that is, a unique identifier associated to a specific transaction.
As for modification requests, the merchant reference value can either:
The number and the type of sub-lines that you need to include.